Traffic signs or road signs are signs erected at the side of roads to provide information to road users. With traffic volumes increasing over the last eight decades, many countries have adopted pictorial signs or otherwise simplified and standardized their signs to facilitate international travel where language differences would create barriers, and in general to help enhance traffic safety. Such pictorial signs use symbols (often silhouettes) in place of words and are usually based on international protocols. Such signs were first developed in Europe, and have been adopted by most countries to varying degrees. Traffic signs can be grouped into several types. For example, Annexe 1 of the Vienna Convention on Road Signs and Signals (1968), which at 30 June 2004 had 52 signatory countries, defines eight categories of signs:
A. Danger warning signs
B. Priority signs
C. Prohibitory or restrictive signs
D. Mandatory signs
E. Special regulation signs
F. Information, facilities, or service signs
G. Direction, position, or indication signs
H. Additional panels
In the United States, Canada and Australia signs are categorised as follows:
Regulatory signs
Warning signs
Guide signs
Street signs
Route marker signs
Expressway signs
Freeway signs
Welcome Signs
Informational signs
Recreation and cultural interest signs
Emergency management (civil defense) signs
Temporary traffic control (construction or work zone) signs
School signs
Railroad and light rail signs
Bicycle signs